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/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
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 */

package java.io;

/**
 * The base class for all writers. A writer is a means of writing data to a
 * target in a character-wise manner. Most output streams expect the
 * {@link #flush()} method to be called before closing the stream, to ensure all
 * data is actually written out.
 * 

* This abstract class does not provide a fully working implementation, so it * needs to be subclassed, and at least the {@link #write(char[], int, int)}, * {@link #close()} and {@link #flush()} methods needs to be overridden. * Overriding some of the non-abstract methods is also often advised, since it * might result in higher efficiency. *

* Many specialized readers for purposes like reading from a file already exist * in this package. * * @see Reader */ public abstract class Writer implements Appendable, Closeable, Flushable { /** * The object used to synchronize access to the writer. */ protected Object lock; /** * Constructs a new {@code Writer} with {@code this} as the object used to * synchronize critical sections. */ protected Writer() { lock = this; } /** * Constructs a new {@code Writer} with {@code lock} used to synchronize * critical sections. * * @param lock * the {@code Object} used to synchronize critical sections. * @throws NullPointerException * if {@code lock} is {@code null}. */ protected Writer(Object lock) { if (lock == null) { throw new NullPointerException("lock == null"); } this.lock = lock; } /** * Closes this writer. Implementations of this method should free any * resources associated with the writer. * * @throws IOException * if an error occurs while closing this writer. */ public abstract void close() throws IOException; /** * Flushes this writer. Implementations of this method should ensure that * all buffered characters are written to the target. * * @throws IOException * if an error occurs while flushing this writer. */ public abstract void flush() throws IOException; /** * Writes the entire character buffer {@code buf} to the target. * * @param buf * the non-null array containing characters to write. * @throws IOException * if this writer is closed or another I/O error occurs. */ public void write(char[] buf) throws IOException { write(buf, 0, buf.length); } /** * Writes {@code count} characters starting at {@code offset} in {@code buf} * to the target. * * @param buf * the non-null character array to write. * @param offset * the index of the first character in {@code buf} to write. * @param count * the maximum number of characters to write. * @throws IndexOutOfBoundsException * if {@code offset < 0} or {@code count < 0}, or if {@code * offset + count} is greater than the size of {@code buf}. * @throws IOException * if this writer is closed or another I/O error occurs. */ public abstract void write(char[] buf, int offset, int count) throws IOException; /** * Writes one character to the target. Only the two least significant bytes * of the integer {@code oneChar} are written. * * @param oneChar * the character to write to the target. * @throws IOException * if this writer is closed or another I/O error occurs. */ public void write(int oneChar) throws IOException { synchronized (lock) { char[] oneCharArray = new char[1]; oneCharArray[0] = (char) oneChar; write(oneCharArray); } } /** * Writes the characters from the specified string to the target. * * @param str * the non-null string containing the characters to write. * @throws IOException * if this writer is closed or another I/O error occurs. */ public void write(String str) throws IOException { write(str, 0, str.length()); } /** * Writes {@code count} characters from {@code str} starting at {@code * offset} to the target. * * @param str * the non-null string containing the characters to write. * @param offset * the index of the first character in {@code str} to write. * @param count * the number of characters from {@code str} to write. * @throws IOException * if this writer is closed or another I/O error occurs. * @throws IndexOutOfBoundsException * if {@code offset < 0} or {@code count < 0}, or if {@code * offset + count} is greater than the length of {@code str}. */ public void write(String str, int offset, int count) throws IOException { if ((offset | count) < 0 || offset > str.length() - count) { throw new StringIndexOutOfBoundsException(); } char[] buf = new char[count]; str.getChars(offset, offset + count, buf, 0); synchronized (lock) { write(buf, 0, buf.length); } } /** * Appends the character {@code c} to the target. This method works the same * way as {@link #write(int)}. * * @param c * the character to append to the target stream. * @return this writer. * @throws IOException * if this writer is closed or another I/O error occurs. */ public Writer append(char c) throws IOException { write(c); return this; } /** * Appends the character sequence {@code csq} to the target. This method * works the same way as {@code Writer.write(csq.toString())}. If {@code * csq} is {@code null}, then the string "null" is written to the target * stream. * * @param csq * the character sequence appended to the target. * @return this writer. * @throws IOException * if this writer is closed or another I/O error occurs. */ public Writer append(CharSequence csq) throws IOException { if (csq == null) { csq = "null"; } write(csq.toString()); return this; } /** * Appends a subsequence of the character sequence {@code csq} to the * target. This method works the same way as {@code * Writer.writer(csq.subsequence(start, end).toString())}. If {@code * csq} is {@code null}, then the specified subsequence of the string "null" * will be written to the target. * * @param csq * the character sequence appended to the target. * @param start * the index of the first char in the character sequence appended * to the target. * @param end * the index of the character following the last character of the * subsequence appended to the target. * @return this writer. * @throws IOException * if this writer is closed or another I/O error occurs. * @throws IndexOutOfBoundsException * if {@code start > end}, {@code start < 0}, {@code end < 0} or * either {@code start} or {@code end} are greater or equal than * the length of {@code csq}. */ public Writer append(CharSequence csq, int start, int end) throws IOException { if (csq == null) { csq = "null"; } write(csq.subSequence(start, end).toString()); return this; } /** * Returns true if this writer has encountered and suppressed an error. Used * by PrintWriters as an alternative to checked exceptions. */ boolean checkError() { return false; } }





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